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Maven’s Minutes: Water storage, part 2: A look at California’s successful groundwater management and banking programs

California has long relied on surface reservoirs to manage the state’s fluctuating water supply as evidenced by the over 1300 reservoirs both large and small that dot the landscape – from Redding in the north to San Diego in the south. However, environmental impacts, evaporation, and other concerns associated with reservoirs and the dams that create them have caused a shift towards groundwater banking as a water storage and management strategy for California.

The Central Valley, especially the southern portion of Kern County, is home to numerous groundwater banking operations which played a critical role during the dry years of 2007 to 2009, recovering over two-million acre-feet of banked supplies to their customers. However, groundwater banking is not just for the wide-open spaces of the Central Valley; when properly managed, the same techniques can be applied to groundwater basins in urban areas, providing a reliable local source of water.

So how does it work? Groundwater banking essentially uses the empty space in aquifers for storage purposes, storing water during wet periods that is later recovered for use during droughts. There are two basic methods for putting water into storage:

Diagram courtesy of the Kern Water Bank Authority.

direct recharge: adding surface water supplies either by using recharge ponds to percolate water into the aquifer or by injection wells to place the water directly there, or

in-lieu agreements: surface supplies are provided to groundwater users to be used in lieu of groundwater pumping, and the amount of water that otherwise would have been pumped becomes the banked water.

The groundwater that is stored is then later recovered from the aquifer when needed through recovery wells.

Groundwater storage has several advantages over surface reservoirs as well as a few potential disadvantages. Groundwater banking projects can often store as much as a surface reservoir but cost much less to construct, and they can have a much smaller environmental impact than a reservoir. Another significant advantage is that once the water is recharged into the water bank, evaporation no longer occurs whereas evaporation losses in a reservoir can be several feet per year. Groundwater storage is flexible enough to respond to seasonal and inter-annual variability and will be an increasingly important tool for managing the state’s water resources in the face of climate change.

Semitropic Water Bank

Among the disadvantages, groundwater banking projects have limited recharge capacity; when floodwaters are high, the limited infiltration rate can preclude them from fully capturing the all high flows. Energy costs for recovering water are a factor, and typically exceed energy costs for reservoirs. Pumping from the aquifer is limited by the pumping capacity of the banking facility and not well-suited to demands that can fluctuate significantly during the year.

GROUNDWATER BANKING IN THE CENTRAL VALLEY

The vast groundwater basin underlying the Central Valley is California’s largest reservoir and an important resource for the productive agriculture industry that farms the land above it.

From the Central Valley Groundwater Study, USGS, 2009Click on the image for the fact sheet.

A 2009 study by the USGS found that over the last four decades, the Central Valley has lost around 60 million acre-feet of water due to overpumping. This has had numerous negative effects such as localized subsidence and increased well-drilling as well as higher groundwater pumping costs.

However, the drawdown in the aquifer does present an opportunity to utilize the dewatered portions for groundwater banking, and agricultural water districts have found ways to take advantage of the resource, particularly in the southern portion of the Central Valley.

In Kern County, virtually all the water districts are involved in groundwater banking to some degree. Some are groups that have joined together to develop a project to improve their own water supply reliability while other projects are partnerships between Kern County Water districts and out-of-county entities who bank their excess water surface water in Kern County and then withdraw it in times of need.

Kern Water Bank

One of the largest of the groundwater banks operating in Kern County is the Kern Water Bank (KWB), which serves Kern County farmers as well as the residents of Bakersfield.

Source: Pacific InstituteClick for their report on improving water management through groundwater banking.

Although it’s one of the smallest in terms of acreage, only occupying approximately 20,000 acres or about 30 square square miles, it’s geology makes it particularly conducive to groundwater banking: The water bank is located on a huge fan-shaped wedge of sand and gravel that forms where the Kern River exits out of the Sierras and spreads out into the grasslands of the southern San Joaquin Valley. Sediments here extend as much as 14,000 feet deep and as a result, the Kern Water Bank can add 460,000 acre-feet per year to its basin and recover up to 240,000 acre-feet per year with the capacity to store over 1 million acre-feet of water.

Jon Parker, general manager for the Kern Water Bank, gave a presentation to the Assembly Committee highlighting the operations of the water bank. There are six participants in the Kern Water Bank; they include water storage districts, an improvement district, and a mutual water company. “The water bank essentially serves these entities, banking supplies for them and recovers those supplies in times of need,” he said.

Mr. Parker then gave a brief history of the Kern Water Bank. in the early 1980s, the Department of Water Resources (DWR) purchased 20,000 acres of land in Kern County to implement a groundwater banking project after conducting a feasibility study. However, DWR encountered many legal, institutional, and political roadblocks to implementing the project including concerns about the State Water Project’s ability to pump Delta water for recharge, questions about the ability to meet water quality standards for pump-in to the California Aqueduct, and an inability of DWR and Kern County Water Authority to reach agreement on measures to comply with Water Code Section 11258.

“There were priority questions on who would be able to use the facility and would Kern River water be excluded from the facility so there were problems there,” said Mr. Parker. “There were endangered species issues, both in the Delta and on the lands themselves, and there were water quality questions, such as arsenic and other constituents in the water that would those prevent us from recovering the water. In 1993 DWR halted all design efforts and developed a revised workplan that provided just minimal activities on the bank.”

Kern Water Bank’s Cross Valley Canal

In 1994, provisions in the Monterey Agreement included a transfer of the property over to designated State Water Project agricultural contractors in exchange for permanent retirement of 45,000 acre-feet of their Table A contract amount. The provision transferred the state’s ownership of the Kern County property to Kern County Water Agency, and then to the Kern Water Banking Authority for local agency development and use as a groundwater bank.

The newly formed Kern Water Banking Authority still had to overcome the roadblocks that had derailed the earlier project. There were three sets of stakeholders to be considered: other users of the basin’s groundwater, the wildlife protection agencies (the Department of Fish and Wildlife and the US Fish and Wildlife Service), and the downstream users of the conveyance facilities that would receive water blended with recovered water from the water bank.

“In 1995 , Kern Water Bank MOU was signed, and that was a critical agreement with local adjoining entities to overcome those institutional issues,” said Mr. Parker. “In 1997, a Habitat Conservation Plan was approved that was a critical agreement to get over issues with endangered species on the land and that has worked extremely well. In 2001, the aqueduct pump in policy was developed, and this was a critical agreement with downstream stakeholders to be able to recover our water. Part of that also included extensive sampling and modeling to demonstrate the program’s effect on downstream stakeholders.”

For a successful groundwater banking program, there must be a suitable aquifer with the right hydrogeologic attributes. The Kern River Alluvial Fan is particularly suited to groundwater banking with the upper 1,000 feet of the aquifer consisting of 50 to 70% or more of sand and no laterally extensive confining or perching layers present. Mr. Parker ran down the numbers: “Specific yield is about 18%, hydraulic connectivity is about 60 feet a day – those are really good numbers. Groundwater quality is generally excellent – average concentrations for arsenic are 3 parts per billion, nitrates are 8 parts per million, and TDS is about 290 parts per million.”

Kern Water Bank’s Cross Valley Canal

Access to supplies and regional recovery infrastructure is critical, said Mr. Parker. Conveyance facilities are needed for delivering water to and from a groundwater banking project and the ability to access surplus flows for recharge is necessary. “We have access to water from the State Water Project via the California Aqueduct which accesses the snowpack in Northern California; we have the Friant-Kern Canal which accesses snowpack from the Central Sierra, and we have the Kern River which accesses the southern Sierra, so we have facilities that access snowpack throughout the state going right past the water bank. That’s a tremendous benefit.”

Delivery of recovered water to water banking participants is accomplished either by direct deliveries via the California Aqueduct or by exchange deliveries. These exchanges can occur either by an upstream participant taking water from the California Aqueduct and the Kern Water Bank returns a like amount into the aqueduct downstream or by an agreement that allows the water bank to use San Luis Reservoir to regulate supplies. “A banking program recovers water slower than it can take it in,” said Mr. Parker. “It’s not like a reservoir where you can dump it out rapidly, so you have to have facilities where you can re-regulate that water to maximize the benefit from a groundwater bank.”

The California Aqueduct at the Kern Water Bank

The quality of the groundwater is also important, said Mr. Parker. Although the banking programs may not deliver water directly to the stakeholders (and the Kern Water Bank does not deliver water to entities south of Kern County), since the recovered water is returned to the California Aqueduct, downstream stakeholders receive a blend of aqueduct water and recovered water. “If we’re going to provide water to one of our upstream participants such as Semitropic Water Storage District, they take water out of the aqueduct north of the bank, and we put a like amount of water back in the Aqueduct downstream – not necessarily at the same time, but matching it on an AF by AF basis – and what happens is the blend goes south. And so if we were to put in poor quality water … the folks down south would have a problem with that.”

“You’re not delivering the water to them; they are getting the chemistry of your water downstream,” Mr. Parker explained. Downstream stakeholders may rely on the water to blend and reduce a constituent present in other supplies, “so you really need to match aqueduct background quality on a constituent by constituent basis or mitigate for it,” he said, noting that the Pump-in Guidelines were developed by DWR and the downstream stakeholders in 2001 and have worked very well.

Recharge pond, photo courtesy of Kern Water Bank Authority

The water bank includes 70 shallow recharge ponds that cover 11 square miles. “Our average recharge rate is 1/3 of a foot a day … we can recharge about 60,000 AF a month,” said Mr. Parker, noting that recharge does decline over time. “In 2005-2006, we recharged for 2 years straight and that number dropped to about 30,000 AF a month; we also had groundwater showing up as surface water in low parts of the water bank.”

Maximum annual recharge capacity is about 500,000 acre-feet and the storage capacity is about 1.5 million acre-feet. “You don’t have a set limit with groundwater storage, but that’s more than a lot of the surface reservoirs throughout the state,” said Mr. Parker. “The Kern County Water Agency has estimated there is about 10 million AF of available storage in the Kern groundwater basin.”

Kern Water Bank recovery well

“We have 84 wells with an average depth about 750 feet,” said Mr. Parker. “The annual recovery capacity is about 240,000 AF at the beginning of a recovery program, so that is about half of our recharge capacity which is why you need the facilities to reregulate your supply.”

The water bank operates under a Habitat Conservation Plan/Natural Community Conservation Plan that was executed in 1997. The HCP provides for the management of water bank lands with the stated dual purposes of accomplishing both water banking and environmental objectives. “For example, rather than having well-groomed ponds that have levees on a four sides, the levees are just on downslope areas, and the upslope areas just feather out in a natural topography so it makes for a very natural setting.”

He noted that a statewide-recognized ornithologist did some studies, with one of his bird counts finding over 35,000 water birds. “He considers the water bank one of the top five freshwater wetlands in the state so it really is environmentally a beneficial program.”

Of the 20,000 acres, only 236 acres have been permanently disturbed for water banking facilities, and water bank activities have helped to reestablish willows, cottonwoods, sedges, and other wetland vegetation and habitat that existed historically throughout much of the southwestern San Joaquin Valley. This upland habitat supports a wide range of species including large populations of raptors, burrowing owls, tri-colored blackbirds, kangaroo rats, rabbits, badgers and coyotes.

Mr. Parker then presented a graph that shows the water bank’s recharge and recovery since the bank was formed in 1995. About 65% of the water banked has come from State Water Project supplies; the Kern River has supplied 21% and the Friant-Kern Canal has supplied 14%. “The total recharge over that period of time has been about 2 MAF and our total recovery has been about 1 MAF, so current storage is about 1 MAF in the bank,” he said.

Participants in the water bank have spent about $40 million on infrastructure, with about 90% of the water banks capital costs being funded by the participants. The water bank’s annual expenses are funded through recharge and recovery expenses that are paid by the user. “For recharge, they are about $9.50 to $16 an acre-foot, and on the recovery side they are $70 to $90 an acre-foot,” said Mr. Parker. “The recovery is more expensive because you need energy to recover the water.”

The MOU sets a percentage of loss due to evapotranspiration at 6% of the gross amount of water recharged to provide assurance that the banking operations will not recover more water than actually recharged, so 94% of the water put into the water bank can be pumped out, he said.

For more information:

Click here for more information on the Kern Water Bank: includes an essay on how the water bank works and a copy of the MOU that created the bank, from Jon Parker’s testimony to the Little Hoover Commission in 2010.

Click here for Improving Water Management through Groundwater Banking:Kern County and the Rosedale-Rio Bravo Water Storage District, from the Pacific Institute.

GROUNDWATER BANKING IN URBAN SETTINGS

The water banks in Kern County provide a useful service to farmers as well as urban agencies who bank their excess water there, but groundwater banking can also occur in urban settings as well. The groundwater basins in Southern California are a critical component in the the area’s drive for regional self-reliance, and groundwater management programs in Southern California are an important element in ensuring the resource remains a reliable local resource for generations to come.

The Water Replenishment District of Southern California and the Orange County Water District are two agencies that manage groundwater basins underlying more than 63 cities and about half of the combined population of Los Angeles and Orange County. The next portion of the water storage hearing highlighted the successful efforts of these two districts to manage their groundwater basins in a sustainable way.

Water Replenishment District

The Water Replenishment District of Southern California (WRD) manages two of the most utilized groundwater basins in Southern California, the West Coast Basin and the Central Basin. The two basins extend 420 square miles throughout southern Los Angeles County and are one of the region’s most reliable sources of water.

“Our agency was formed under the Water Replenishment District Act of 1955, AB 2908, that was signed by then-Governor Goodwin Knight,” began Ted Johnson, chief hydrogeologist for the Water Replenishment District. “To my knowledge, we are the only water replenishment district formed under this act … which defines a special district to put water into the ground. Not necessarily to take it out and serve it for drinking water, but to put it under ground and store the water.”

The Water Replenishment District is a public agency with five board members elected by the public to four year terms. “We operate under Division 18 of the California Water Code, and our mission is to put water back into the aquifers that other entities are pumping out at a more rapid pace than can be refilled naturally, so we provide artificial replenishment water to fill up and make up the deficit,” he said. The WRD is also involved in groundwater monitoring, safe drinking water programs, and combating seawater intrusion throughout Southern Los Angeles County.

The Water Replenishment District has 43 cities within its boundaries and serves 4 million people – over 10% of the state’s population, he said. “In our service area, about 60% of the water is imported, either from the Colorado River or through the Bay-Delta in Northern California, but 40% is still groundwater from local wells,” said Mr. Johnson.

The groundwater basins contain multiple aquifers in layers of sand anywhere from 50 feet to hundreds of feet thick which are separated by layers of clay. “The water wells that go down and tap every good aquifer they can find and they might go down over 2000 feet deep,” said Mr. Johnson. “Below those aquifers are the bedrock, so that defines the extent of our groundwater basins, and our job is to try and pour water into these things and fill them back up as those 43 cities are pumping out water from their wells.”

There are over 400 active wells pumping from the groundwater basins. “From Los Angeles to Downey to Long Beach and Lakewood, and over on the Westside with the city of Torrance and Manhattan Beach, they all have wells that are pumping out groundwater,” said Mr. Johnson. “We have a Geographic Information System or GIS that helps us map where all of those wells are located. Each one of those wells, they have to pay us a fee as they pump out groundwater, and we use that money to buy water and put it back into the ground, so it is the users of the groundwater that are paying for us to replace the groundwater and that’s a good system. If you don’t pump any groundwater, you don’t have to pay us. If you pump a lot of groundwater, you have to pay us a lot so we can put the water back into the ground.”

Prior to the formation of the District in 1959, over-pumping caused many water wells to go dry and allowed sea water intrusion to contaminate coastal groundwater. “Groundwater pumping as development occurred was quicker than Mother Nature could replace the water,” said Mr. Johnson. “The hydrographs show water levels going to a high and just plunging down uncontrolled; we saw 160 feet of draw down in the water table, which is about 8 feet per year and wells were going dry.”

The water table dropped so low it went below sea level. “When you’re next to the ocean and your water table is below sea level, that just allows the ocean to pour in underground, and contaminate the fresh water with salt water, and so we had a real problem with seawater intrusion which was wrecking our groundwater supply,” he said.

If left unchecked, it would have been a disaster for the Los Angeles region to lose such a valuable water resource, he said, but three things occurred to fix the problem. First, wells were installed along the coast to combat seawater intrusion. “Hundreds of wells along the coast exist today that are constantly pumping fresh water into the ground to stop the ocean from coming in,” said Mr. Johnson.

Second, the Water Replenishment District was formed in 1959. “We were enacted to make up the difference between Mother Nature’s water and what the shortage was,” said Mr. Johnson. “Our mission is to buy supplemental water whenever we can find it and as cheaply as we can find it and stick it underground. So we do modeling and contour maps and analysis to see how much water we need to buy and put into the ground every year. That is our main job.”

Lastly, in the 1960s, the two groundwater basins were adjudicated to control the amount of pumping. “That got rid of the wild cat anybody could pump whatever they want kind of pumping, and instead, put a limit and told each entity, each city, how much they could pump,” said Mr. Johnson. “And they are held to that today, but it’s still more pumping than Mother Nature gives us and that’s why our job is to put water back into the ground in storage.”

Afterwards, with the sea water barriers, the groundwater recharge and the controlled pumping, water levels have returned to healthy levels now, saving the groundwater resource, said Mr. Johnson. “In fact, we’ve put in over 7 MAF into storage since that time which could provide enough groundwater for 28 years of pumping, so it is the groundwater storage programs that really has allowed continued use of these groundwater basins and will so in the future.”

San Gabriel Spreading Grounds

The easiest way to put water into the ground is to let gravity do its work. “You pour water on the ground and it soaks in, but you can only do that in certain areas so it has to be geologically suitable,” he said. “You have to have sandy soil and you have to have thorough geological investigations to see if you can even have this water go down.”

The Rio Hondo and San Gabriel Spreading Grounds, located in the cities of Montebello and Pico Rivera, are situated over a geologic uplift in the Central Basin that allows surface water to percolate into the aquifers below ground. The spreading grounds collect local stormwater runoff, important water and highly treated recycled water for recharging the aquifer.

Injection wells are another way to get water into the ground. The seawater barrier wells along the coast are an example of this; fresh water is pumped down hundreds of feet to keep the sea water from intruding, he said.

In-lieu programs that pay groundwater pumpers to use surface water from Metropolitan instead: “When water is plentiful for Metropolitan and water is cheap, we’d rather have them take the Met water than take the groundwater, so that’s another way to put water into storage.”

WRD’s general manager is a professional engineer and of the 31 staff, half of them hold engineering or science degrees, said Mr. Johnson. WRD conducts groundwater monitoring, modeling and planning to monitor the health of the basin as well as prepare for future conditions. “You have to know a lot about the technical details of putting the water in, the specific capacity, the hydraulic permeability and all of these other issues, so it’s important to have a lot of good science behind groundwater storage,” he said.

There is a long list of things that we look at as hydrogeolists, he said. “You need to know where your aquifers are, how big they are, how deep they are, where are the best places to put water into the ground, and what damage might happen if you put it in at the wrong place. You might have a Superfund site nearby and you don’t want to put your good, freshwater in with superfund water and contaminate your water, so you have to be very careful where you put in your water for storage.”

The district uses multiple tools to monitor conditions in the groundwater basin. “We have a very extensive groundwater monitoring program that we have put in with over 300 monitoring wells all throughout the basin,” he said. “Monitoring wells are our eyes into the underground so we have to drill wells, find out where the water is, test its quality, take the aquifer test to know what the permeabilities are, and after that we can figure out where the water is going to go.”

The district also uses extensive computer models, geophysical logs, and geographic information systems, as well as GeoTracker data from the State Water Board which identifies contaminated sites, and the CASGGEM system for monitoring short and long term groundwater levels throughout the basin.

“For the future, we’ve identified over 450,000 acre-feet of space just kind of sitting there; it’s like an empty safe deposit box that we want to fill up with water and we’re looking for ways to do that,” he said. “If we can tap into that 450,000 acre-feet, we could drought-proof the region and have a long term water supply.”

The district used to rely on imported water from the Delta, but not so in recent years. “Metropolitan doesn’t have the surplus that they used to and the costs are going through the roof, so we’re having to develop our own sources of water to replace the Met water we used to use,” he said. “We use any source available. We use a lot of recycled water from the wastewater plants. We use local stormwater by building rubber dams and capturing that water. We treat Superfund water and make it pure and then put it back into the ground … so there’s a lot of other water you can use for groundwater storage.”

WRD’s Leo J. Vander Lans Advanced Water Treatment Facility

“If we were to buy imported water today, it is about $700 an acre-foot – and that’s just for untreated raw river water from the Delta,” said Mr. Parker. “The recycled water from the sewage treatment plant next door is $40 an acre-foot, and it’s just as clean, it’s just as good, so we love that recycled water from those wastewater treatment plants,” noting that the district follows the health department’s regulations for putting recycled water into the ground.

The Water Replenishment District has a program called WIN, or Water Independence Now, the purpose of which is to completely eliminate dependence on imported water by developing local sources. “By using more recycled water and more storm water, we’ll be able to put storage water in there without using imported water,” he said. “That will help save the Bay Delta because we won’t need the Bay Delta water anymore which will free it up for other uses.”

There are both technical and non-technical challenges for the Water Replenishment District. “The technical challenges are all about the science – you need to have open space, you need to have the geology, you need to have the hydrogeology, you need to have the water quality, and that’s very important to study,” he said. “In urban Los Angeles, we don’t have 11 square miles of open land to put water into the ground so we have to be more creative with injection wells and other opportunities.”

WRD’s Leo J. Vander Lans Advanced Water Treatment Facility

The non-technical challenges can be even more challenging, he said. “There are a lot of litigation actions – we’ve been ten years in litigation on groundwater storage issues. We like to unfortunately joke that the courts are getting more action than our aquifers.” He noted that last year, SB 1386 by Senator Lowenthal passed that helped settle a long-term legal dispute. “It defined who gets to do groundwater storage, so it put to bed the competitiveness and the litigation of multiple agencies fighting over who would control storage.”

So in conclusion, “The Water Replenishment District has demonstrated as others have that groundwater storage works and it works well, and it can save groundwater basins; it’s a proven method, there’s nothing magic about it and it’s a benefit,” said Mr. Johnson. “But you have to do it with caution and you have to know what you’re doing. Increasing recycled water and stormwater is a benefit to Bay-Delta water and will help save the Delta for other uses if our local groundwater agencies can use our own water and be self-sustainable. Proper science is needed to fully understand the ramifications of what you’re doing, and we feel a lot of those challenges can be overcome with a lot of education and discussion and help from friends as needed.”

For more information:

Orange County Water District

Roy Herndon, Chief Hydrogeologist from Orange County Water District spoke next about the successes and challenges of storing water in their District, noting that while they do some similarities to the neighboring Water Replenishment District, there are some differences as well.

The boundaries of the Orange County Water District cover only the north half of the county, not the entire county. “We have about 2.4 million people that live in our water district, so that is the most populated part of Orange County; the area gets about 70% of its supply of water from the groundwater basin,” he said. The groundwater basin can hold between 10 million and 40 million acre-feet of water, of which about 1.5 million acre-feet is usable.

However, in the southern part of the county, less than 5% of total supply comes from groundwater because there are few groundwater basins in that area, “so it really is the geology that makes the difference between the northern half of the Orange County and the southern half of Orange County.”

The agency was formed by the legislature in 1933 with the mission to manage the groundwater basin under Orange County that now serves water to more than 20 cities and water agencies which in turn serve more than 2.3 million Orange County residents. “That is our purpose in life,” said Mr. Herndon. “We are not a retail agency. We manage the aquifer, we replenish it, we have recharge facilities, and we have seawater barriers.”

The district has a 10 member board of directors of which seven are publicly elected and three are appointed, he said. “We get our revenue from charging an assessment on the amount of water that is pumped from the production wells much like the Water Replenishment District. Our major source of revenue is from water users.”

The District has a number of programs to protect water quality. “We are cleaning up some groundwater contamination plumes that have been abandoned and a number of other projects that we’re working on to protect and keep this groundwater basin sustainable,” he said.

There are over 200 production wells that draw water from the basin. “These are large capacity city wells owned by cities such as Anaheim, Santa Ana, and Orange,” said Mr. Herndon. “They are the ones that own the wells; they pump the groundwater and they sell it to the residents and the businesses in their cities. They are essentially our customers. Our job is to manage the basin so they can rely on it for up to 70% of their water supply.”

When the Orange County Water District was first formed in 1933, 86% of its customers were agricultural. “We have very few farmers at this point. It’s almost all urbanized; there is very little farming left in the basin to speak of,” he said. “In some respects, I think that makes things easier for us.”

Water enters the groundwater basin via settling or percolation ponds in the cities of Anaheim and Orange and along the Santa Ana River. “We take water and we percolate it through the river bed, and we also divert water from the river into old gravel pits and that water percolates into the aquifer,” he said.

The groundwater basin has three major aquifer systems; a shallow, a middle and a deep zone. “The middle zone is where most of the wells pump water from; they are typically about 1000 to 1200 feet deep,” he explained. “Our recharge water comes in from the inland areas through the river and the percolation basins and spreads out vertically into the different aquifers, and replaces the water that’s pumped out on an annual basis. We also inject quite a bit of water for sea water intrusion; similar to Water Replenishment District, we use quite a bit of recycled water to do that.”

Mr. Herndon then presented a time series graph showing the amount of available storage in the groundwater basin dating back to 1969. “This illustrates how we empty and fill the basin just like a reservoir,” he said. “This underground reservoir has taken us through four different drought periods. We draw the basin down in a drought, and when we have some wet periods and we have available surface water, we refill the basin, just like you would any other reservoir. We know that if we manage it properly, we can take it down, draw it down, but we need to bring it back up.”

Mr. Herndon said that 500,000 acre-feet has been established as the bottom end of the range. “We have established an operating range for our basin through trial and error and understanding our basin. Sea water intrusion is a major issue for us. If we go below 500,000 acre-feet, we can’t control sea water intrusion.”

The District primarily recharges the basin with water from the Santa Ana River and, to a lesser extent, with imported water purchased from the Metropolitan Water District of Southern California. The District currently holds rights to all Santa Ana River flows that reach Prado Dam: “We get our recharge water from the Santa Ana River through storm flows which happen during about 2 or 3 months out of the year, although not this year, I’m afraid, as it’s been a very dry year for us,” said Mr. Herndon. “And base flows, which are essentially upstream discharges of treated sewage effluent coming down the Santa Ana River. We divert that water and percolate it where it’s then filtered and it’s very good drinking water quality when its pumped out of the production wells.”

“A lot of that base flow water is essentially upstream effluent from treatment plants and the upstream agencies are doing more and more to capture that water and use it for themselves, instead of dumping it in the river for us so we’re having to make changes and accommodate that or handle that,” he said. “Imported water has historically been a good source of recharge water during times of surplus; however, as Ted mentioned, that imported water is now declining. With the Bay Delta and the endangered species issues, we’ve seen our imported supply for recharge drastically drop, so how we’re compensating for that is by recycling more water in a very highly treated process and that is how we’re making up for the loss of imported water.”

The District has 1100 acres of infiltration basins, which is a little less than 2 square miles. “We put a lot of water in the ground in a very small area so we have some very high percolation rates that we’re able to sustain in our spreading basins,” he said. “We and the sanitation district partnered to build a $480 million water recycling project that we call the Groundwater Replenishment System,” noting that the system recharges about 20 to 25 percent of all the water that is pumped out of the basin or about 70,000 acre-feet. “That’s been a big project that is cost-effective compared to imported water.”

Sea water barriers inject about 30,000 acre-feet per year through injection wells, and the District has a stormwater storage agreement with the Army Corps of Engineers to hold water behind a dam upstream and release it more slowly so we can get that water into the groundwater basin, he said.

“We couldn’t do it if we didn’t have cooperation from our pumpers,” he said. “The agencies report all their pumping so we know how much is being pumped out of the basin and we know how much we’re putting in so at any given time, so we know how much water is being stored in our basin.”

There are over 500 monitoring wells throughout our basin so it is well understood and well characterized. “Similar to Water Replenishment District, we have a highly skilled and dedicated staff,” he said. “We have a long term need for that kind of skill set and we hire people to handle and understand this.”

The economic benefit of using groundwater instead of imported water is significant, Mr. Herndon pointed out. “For the City of Anaheim, to buy an acre-foot of treated, drinkable water, either from the Colorado River or Northern California, it is $900 an acre-foot,” he said. “Our groundwater, after they pump it out and deliver it into their system, is $430 an acre-foot, so it is less than half the cost. When you multiply that by the amount of pumping in the basin – 300,000 acre-feet per year, there is a $141 million economic benefit by using the groundwater basin versus imported water, and that’s an annual savings to the producers.”

Of the $430 an acre-foot, the District charges currently $266 an acre-foot; “That’s our charge to manage the groundwater basin and put water back in the ground, so the rest of the cost is the energy to lift it out of the ground and to send that water into the producers retail system.”

“It pays for itself, and that’s why we were able to build that $480 million recycled water project because it offsets $900 an acre-foot imported water,” he said. “We built that project and it’s approximately $700 an acre-foot fully loaded cost, so it is cost effective to do recycling in our area versus import.”

FOR MORE INFORMATION ON THIS HEARING AND GROUNDWATER BANKING:

EXPLORE FURTHER:

Water marketing and groundwater banking go hand in hand: The PPIC report, California’s Water Market, By the Numbers:Update 2012, discusses the importance of both water markets and groundwater banking as tools for dealing with the uncertain conditions of the future: ” …For many water managers, groundwater banks and water markets are complementary tools for accessing and managing supplies. A well-functioning water market also facilitates groundwater banking, because it enables managers to purchase and bank additional water for later use. Likewise, well-functioning groundwater banking programs can augment the volume of water available for lease or sale by moving water from wetter to drier periods. Both the water market and groundwater banks help tie together California’s often fragmented water infrastructure, and they increase incentives for local water managers in different parts of the state to cooperate. … ” Read more here: California’s Water Market, By the Numbers:Update 2012

Coming up in Part 3: Gwyn-Mohr Tully and Tim Parker discuss how to optimize surface and groundwater resources.

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